This invention relates to a system for supporting a work platform in a desired position underwater. More particularly, it relates to a system which can stably support an underwater work platform when the support system itself is undergoing motion.
Various methods are used for supporting equipment underwater while performing operations such as pipe laying and repair, cable installation, and salvage work. These include suspending the equipment from a surface vessel by means of a crane using a single cable, supporting the equipment on a legged structure mounted on the sea bottom, and mounting the equipment on a submersible. However, each of these methods has severe limitations. Equipment supported by a crane from a surface vessel is subjected to all the motions that the surface vessel undergoes, so it is difficult to control the position of the equipment. A legged structure mounted on the sea bottom can provide stable support for underwater equipment, but the legged structure will normally disturb the sea bottom, creating turbulence that hampers underwater operations and possibly damaging the work site. Furthermore, the depth of the water in which legged structures can be employed is limited. Submersibles have great dexterity and mobility, but they are expensive to manufacture and have a small payload to weight ratio.
Accordingly, there is a need for a support system capable of supporting equipment underwater in a stable manner. There is also a need for a support system that it economical to manufacture.